I am trying to come up with some plot description which would not have too much spoilers - the book blurb has some fairly big ones - but I am not sure I can do it given that this is the second book of the series. 14-year-old Lily and her brother Silas are stuck in a very gloomy and dreadful place called Nightfall Gardens with Lily living inside the similarly named mansion and Silas outside with a group of protectors called the dusk riders. The first book ended with big cliffhangers for both siblings; this one starts right where the previous left off. The structure of the book is still the same: each chapter is told from Lily's and her brother Silas' POV in turns and each chapter ends in a mini-cliffhanger.
I am quite positive that if someone looks the definition of "severely underrated trilogy", the series' picture would be there. I have yet to see a more interesting story with so few people who read it. This book just like the first one kept me from getting much-needed sleep at night as a thought about putting it down and going to bed has not even come to me at all during my reads. By the way, if you hear a strange noise while reading this review, it is me kicking myself for not reading this sooner as I finished the first one quite a while ago, but was too busy with other reads.
Do not let the young age of the siblings fool you: the story is for adults as well. In fact it became even darker in this book. My final recommendation is the same as before: go and give the first book a try. Now.
This review is a copy/paste of my BookLikes one: http://gene.booklikes.com/post/954410/the-middle-book-of-one-of-the-most-underrated-series-does-not-suffer-from-a-middle-book-of-a-trilogy-syndrome